Even 'cold' permafrost zones vulnerable to thawing

December 14, 2016

George Burba photo. Thawing ice wedges and permafrost are altering the Arctic landscape.

University of Alaska Fairbanks scientists are presenting their work at the American Geophysical Union’s fall meeting in San Francisco this week. Here are some highlights of their research, as shared at the world’s largest Earth and space science meeting.

Climate change is altering the landscape even in permafrost-covered regions that are projected to maintain cold temperatures for many decades, according to University of Alaska Fairbanks researchers.

University of Alaska Fairbanks researchers Skip Walker, Louise Farquharson, Bill Cable and Anna Liljedahl reported during an AGU presentation on Wednesday that studies have observed significant thawing in numerous sites in the high Arctic in recent years.

Farquharson, a doctoral student in the UAF Department of Geosciences, discussed the state of “very cold permafrost” in the Canadian Arctic, where long-term models predict continuous permafrost will remain into the late 21^st century.

Researchers monitored three high-latitude test sites between 2004 and 2016. The study found that all had significant ice-wedge degradation, even though they have mean annual ground temperatures that are well below freezing. The thawing caused the ground to subside by as much as 90 centimeters in some areas and created significant pooling.

Each of the test sites had ice close to the surface with no intermediate layer of ground cover, conditions that are common in the high Arctic. That “naked” state leaves the ice vulnerable when seasonal temperatures rise above freezing, Farquharson said, much like permafrost in warmer areas with insulated vegetative cover.

Based on those results, Farquharson said the vulnerability of cold-region permafrost may need to be examined more closely in future climate change projections.

“We see this pretty drastic shift,” she said. “I think it’s important to begin considering where this will go in the next century.”

Anna Liljedahl, an assistant research professor at UAF’s Water and Environmental Research Center, discussed a separate study that tracked conditions at 11 test sites in Russia, Canada and Alaska. The tops of ice wedges melted at those sites during warm periods, even though the sites had annual mean temperatures below freezing.

The thawing was significant enough that it encouraged drainage and runoff, conditions that could lead to an overall drying of the landscape.

Liljedahl said stability isn’t ensured by below-freezing mean temperatures in continuous-cold permafrost zones. In 2011, for example, an unusually warm summer led to significant degradation of ice wedges.

“In order for us to project changes in the Arctic in the future, we need to look at events — extreme warm summers and changes in the landscape due to permafrost degradation,” she said.